Beat the egg yolks with the caster sugar until thick, then add the walnuts
and orange rind and juice and stir in the self-raising flour. Whisk the
egg whites until stiff, then fold them into the mixture and turn into a
greased and lined 18 cm/7 in square cake tin (pan). Bake in a preheated
oven at 180°C/350°F/gas mark 4 for 45 minutes until springy to the touch.

To make the sauce, beat together the butter or margarine, brown sugar and
plain flour in a saucepan, then heat gently until the butter melts and the
mixture bubbles. Cook for 4 minutes, stirring continuously. Stir in the
milk and bring to the boil, stirring continuously, until the sauce is
thick and smooth. Serve the pudding warm with the hot sauce.